1. Field of the Invention
This invention relates in general to measuring evaporation rates in bodies of water, more particularly to using evaporation pans to measure evaporation rates, and most particularly to evaporation pans employed within the body of water to measure evaporation rates.
2. Description of the Related Art
It is important for maintenance of wetlands and certain waterways to periodically obtain estimates of evaporation for these open waters. Most often the biggest source of error in a lake, wetland, or lagoon is the estimate of evaporation. Currently, there are numerous methods of obtaining such estimates of evaporation. One inexpensive method is to put water in an evaporation pan near the water body being evaluated. As the water evaporates from the pan, measurements are taken to determine the evaporation rate.
However, there are several problems associated with obtaining accurate evaporation rates using this method. First, due to the pan being placed on land, the water temperature within the pan could be far greater than the water temperature in the water body being evaluated, causing evaporation to be over estimated. Second, vegetation, wind patterns, soil type, and moisture content on land also greatly affect evaporation rates.
One method developed to alleviate these problems is to place the evaporation pan in the actually water body being measured by placing the pan on a raft anchored with ropes tied to land or weights placed in bed sediment. However, accuracy problems still exist using this method. Because the raft is normally constructed of wood or plastic, these materials absorb heat and transfer the heat to the pan/water, raising the water temperature in the pan to above that of the water body. Also, the raft raises the pan so the water level in the pan is much higher than the water body being evaluated, again, potentially affecting the evaporation rate determination. Still further, attaching a rope to one side of the raft has a tendency to make the raft tilt in one direction, causing the pan and water to be tilted, yet again, potentially affecting the evaporation rate results.
Therefore, it is desired to provide an apparatus and method to obtain a more accurate evaporation rate in open bodies of water that is inexpensive and easily deployed in the field.